These studies will utilize organ cultures of embryonic rat and chick lung tissues to study extracellular matrix synthesis, and the role of the matrix components in bronchial development. The types, relative proportions, and organization of collagen, proteoglycans and basement membranes synthesized in developing lung tissues will be determined, and the cells synthesizing these macromolecules will be identified. Characterization of the extracellular matrix components will be done with electron microscopy, autoradiography, immunochemical staining, and biochemical analyses. In addition, the effects of micro-environmental factors such as tissue oxygen levels, ion concentrations, exogenous macromolecules, and various pharmacological agents on extracellular matrix synthesis, bronchial morphogenesis, and the visco-elastic properties of developing lung tissues will be examined. These studies will contribute to our understanding of (1) the regulation of lung development, (2) the role of extracellular matrices in the maintenance of airway shape and continuity, (3) the effects of conditions such as hypoxia on connective tissue matrix synthesis, and (4) the relationship between the static and dynamic length-tension characteristics, and the extracellular matrix components in the developing lung.